1. Field of the Invention
The present invention relates to a printing apparatus and a printing method.
2. Description of the Related Art
A conventional printing apparatus performs printing in a monochromatic print mode when a print page includes monochromatic image data, and in a color print mode when a print page includes color image data. As a conventional printing method used in a printing apparatus, an electrophotographic system and an inkjet printing system are known.
For example, in an electrophotographic printing apparatus, in a monochromatic print mode, a toner image of a single color (for example, black) is transferred onto a sheet before pressure and heat are applied to the sheet, and the toner image is fixed on the sheet. On the other hand, in a color print mode, toner images of plural colors (for example, four colors of yellow, cyan, magenta, and black) are fixed on a sheet. In a color print mode, toner images of plural colors are fixed on a sheet overlapping with one another. Accordingly, in the color print mode, it is necessary to apply sufficient heat to a sheet at a sheet conveyance speed which is lower than a sheet conveyance speed of the monochromatic print mode.
As described above, in a printing apparatus, sheet conveyance speeds are different between a monochromatic print mode and a color print mode. In such a type of printing apparatus, the following problem arises in performing a print job including both monochromatic image data and color image data. That is, when both monochromatic image data and color image data are present, a print mode needs to be changed during print processing. Thus, additional time is consumed to execute a print mode changing operation. Accordingly, printing efficiency is lowered.
In order to solve this problem, Japanese Patent Application Laid-Open No. 10-63450 discusses a method which selects print modes. When a print job including both monochromatic image data and color image data is performed, it is determined which print mode is better to be selected in terms of printing efficiency.
The method discussed in Japanese Patent Application Laid-Open No. 10-63450 has the following problems.
In the method used for a printing apparatus discussed in Japanese Patent Application Laid-Open No. 10-63450, a print mode is selected considering in advance whether image data is color or monochromatic as to all pages when image data for plural pages are printed. Consequently, in this method, print processing cannot be started before determining whether image data is color or monochromatic for all pages.
In another conventional method, a print mode can be selected without determining whether image data is color or monochromatic for all pages, in order to quickly start print processing. In such a method, when a color print mode is selected, processing for shifting to color printing is performed to change a printing apparatus to a state in which color printing can be performed. In the processing for shifting to color printing, it generally takes longer time than processing for shifting to monochromatic printing that is performed to shift a printing apparatus to a state in which monochromatic printing can be performed when a monochromatic print mode is selected.
However, when a color print mode is selected, it cannot be previously determined whether a print job includes color image data. Accordingly, a print job can be completed without print processing of color image data although a color print mode is selected.
In such a case, processing for shifting to color printing is performed even on a print job that does not include color image data. As a result, the shifting to color printing is uselessly performed and causes a waste of time.